Thin client is a generic name of a system in which main processing of a computer is executed in a server with respect to processing requested by a user, so that a terminal client executes minimum processing such as input/output.
Merit of a thin client is preventing information leakage by not having data in a terminal client to improve productivity through application of a security patch in the lump to a server by an expert staff officer.
Since the system can be used irrespectively of a place where a terminal client is disposed, it is possible to cope with disaster control measures and various work styles.
It is also possible to reduce costs in the entire thin client while realizing a high security level and high availability by investing only to an in-house server having data.
On the other hand, while a thin client has a low total cost because a long-term operation cost is low, an introduction cost may be higher than that of a system using ordinary computer and network.
Accordingly, when using a thin client environment while avoiding high introduction cost, service called DaaS will be used at a meter rate.
Appearance of the service is shown in FIG. 16.
FIG. 16 is a diagram showing service of lending a thin client environment according to the background art. The service comprises a thin client environment 610 including a virtual machine 650 and a virtual machine terminal 630.
The virtual machine 650 has a function of executing actual processing of a computer. The virtual machine terminal 630 has a function of executing input/output for the processing of the virtual machine 650. The thin client environment 610 represents that a tenant user operates the virtual machine 650 by the virtual machine terminal 630.
The tenant user connects to the virtual machine 650 through a remote network 620 and a tenant network 640 in a data center by using the virtual machine terminal 630. For the connection, used is an RDP (Remote Desktop Protocol) protocol or an ICA (Independent Computing Architecture) protocol, for example.
The virtual machine terminal 630 is a dedicated terminal or terminal software operable thereon which is realized by a real computer or a virtual computer having at least a CPU (Central Processing Unit), a memory, an input device such as a mouse or a keyboard and an output device such as a display.
A remote network 620 is a network leading to a data center 600 from the virtual machine terminal 630 and is realized by VPN (Virtual Private Network) connection to the data center 600 from an internal network in an office of a tenant, for example.
The tenant network 640 in a data center, which freely communicates with a virtual machine of a tenant and cuts off connection from other tenant, is realized by equipment such as a physical cable switch router or virtual network software.
The virtual machine 650 is a virtual computer operable on a hypervisor. After connection, input through an input device of the virtual machine terminal 630 and output through an output device of the virtual machine terminal 630 which are executed from/to the virtual machine 650 realize the thin client environment 610.
Mechanism of the data center tenant network 640 in the data center 600 is shown in FIG. 17.
The virtual machine 650 has a virtual NIC (Network Interface Card) 724 and at the time of communication via a physical NIC 727 of a hypervisor 720, executes VLAN-setting at a VLAN group setting unit 726.
When using a tag VLAN with the Ethernet mounted, for example, VLANID is set at an Ethernet frame. An Ethernet frame is transmitted to a physical NIC 713 of a layer 2 switch 710, is delivered in a VLAN 712 formed by the layer 2 switch 710, is passed from the physical NIC 713 of the layer 2 switch 710 through the physical NIC 727 of the hypervisor 720, has the VLAN setting released at the VLAN group setting unit 726 and is received by the virtual NIC 724. Accordingly, the VLAN group realizes the tenant network 640 in the data center.
As described in the foregoing, a virtual machine used by a tenant in the service of lending a thin client environment operates on a hypervisor managed by a service provider. In a thin client environment, a virtual machine in a tenant is allowed to freely communicate to do a job.
Since a tenant needs no equipment to be owned by itself, it is possible to reduce introduction costs, as well as putting operation of equipment into a charge of a highly reliable data center, resulting in increasing business continuity.
Since a service provider manages a large-scale thin client environment at a data center, operation costs will be intercepted. Therefore, cost cutting is realized by sharing equipment for use in a thin client environment among tenants.
On this occasion, unless network confidentiality is ensured among tenants, communication of other tenant will be received. However, since a thin client environment is prepared as soon as a tenant requires, it is impossible to set a network at equipment of a data center in advance, so that every time the tenant asks for a thin client environment, the network will be set on demand.
In other words, security setting of a network to be connected to a hypervisor in which a virtual machine is to be generated should be executed for the first time when creating a virtual machine.    Patent Literature 1: Patent Laying-Open No. 2010-062738    Patent Literature 2: Patent Laying-Open No. 2000-134248
In the Patent Literature 1, used as a method of setting up a tenant network in a data center on demand is VPN. In the tenant network in a data center, a virtual machine is connected by a mesh topology VPN, which makes communication between virtual machines of the tenant be possible to have accessibility and makes communication between virtual machines of other tenant be impossible to have confidentiality. The Patent Literature 1, however, has the following two problems.
First, since for a number n of virtual machines, two to the power of n of VPN tunnels are required, the amount of time calculation will be O(2^n), so that the larger the number of virtual machines becomes, the longer time the processing takes.
Secondly, because tenants are discriminated by an IP address, it is technically impossible for a virtual machine of other tenant to use the same IP address, so that sharing a thin client environment among tenants will involve limitation that the same IP address cannot be used by other tenant. Therefore, at the time of providing service for a thin client environment, VPN is not practical as a method of setting up a tenant network in a data center on demand.
In the Patent Literature 2, used as a method of setting up a tenant network in a data center on demand is VLAN. Since a layer 2 switch has an external interface for setting up a VLAN and a network segment is logically divided by the VLAN, communication between virtual machines of the same tenant is possible to have accessibility and communication between virtual machines of other tenant is impossible to have confidentiality.
Since each layer 2 switch has an independent VLAN structure, structuring a VLAN with a plurality of layer 2 switches causes connection to VLAN of other tenant to lose confidentiality. Therefore, it is necessary to avoid overlapping of a VLAN among tenants within the same network segment, for example.
Thus, at the time of setting up a tenant network in a data center on demand when generating a virtual machine, issues to be resolved are (1) reduction in the number of networks which execute work and management of equipment which actually generates a virtual machine, (2) realization without using an IP address and (3) coexistence of accessibility and confidentiality in a tenant network in a data center.
Issues to be resolved in the service of lending a thin client environment not considered in the Patent Literature 1 and the Patent Literature 2 are (4) the need of facilitating expansion of a hypervisor in a data center when a hypervisor in which a virtual machine is to be generated runs short and (5) the tenant's need of managing a virtual machine by OS information, for example, a domain suffix, at the time of using the service.